Load He triplet modifier coefficient tables
he_modifier_init ([; <qualifiers>])
This function initializes a number of internal data structures by reading tables of coefficients from FITS files on disk. If called with no arguments, the default coefficient tables are loaded.
Paths to specific data files may be specified using qualifiers
collex for collisional excitation coefficients, and
photoex for photoexcitation coefficients.
The coefficient tables currently included in the distribution are:
he_modifier_chianti.fits:
Coefficients for triplet emissivities vs. density for a
grid of temperatures, derived from Chianti.
he_modifier_apec.fits:
Coefficients for triplet emissivities vs. density for a
grid of temperatures, derived from a custom APEC run.
he_photoex_modifier_chianti.fits:
Coefficients for triplet emissivities vs. photon density
for a grid of temperatures, derived from Chianti.
he_modifier_init ( ;collex="he_modifier_chianti.fits",
photoex="he_photoex_modifier_chianti.fits");
Compute He triplet line emissivities for a given (Z,n,T)
Struct_Type = triplet_line_em (Z, ndens[], temp[] [;<qualifiers>])
Compute the He triplet line emissivities for element, Z (an
integer), number density, ndens, and Kelvin temperature,
T. ndens and T may be one-dimensional arrays.
The return value is a structure of the form
struct {Z, ndens, temp, w, x, y, z}
Z is an integer, ndens and temp are
arrays of length nn and nT, respectively.
The struct fields w, x, y and z
are arrays of dimension [nn,nT] containing the line
emissivities.
If the db_norm qualifier is present, the triplet line
emissivities will be normalized so that the total emissivity
w+x+y+z matches the value from the currently loaded
spectroscopy database rather than the value from the relevant
coefficient table. Note that the total emissivity has little
dependence on density.
If the photoex qualifier is present, the ndens
parameter must be the photon energy density.
% Compute Ne IX line emissivities on a 2D
% density-temperature grid:
ndens = 10^[8:15:0.1];
temp = 10^[6:8:0.05];
s = triplet_line_em (Ne, ndens, temp);
plot (log10(s.ndens), s.z[*,0]);
plot (log10(s.temp), s.z[0,*]);
Define a custom He triplet modifier function
create_he_modifier (name [, elements] [; photoex])
Define a custom He triplet modifier function called name.
The modifier function can then be used in conjunction with a
custom spectral model function created using
create_aped_fun.
The optional second argument can be used to limit the modifier function's effect to the elements given in a space- or comma-delimited string of element names. Otherwise, all elements found in the coefficient database will be affected.
If the photoex qualifier is present, the new modifier
function will represent density dependence associated with
photoexcitation. Otherwise the modifier function will represent
pure collisional density dependence.
% Include collisional density dependence for
% Ne, O, and Mg triplets only:
create_he_modifier ("He_a", "Ne,O,Mg");
create_aped_fun ("my_model", default_plasma_state);
fit_fun ("my_model(1, He_a(1)) * wabs(1)");
% Include photoexcitation density dependence for
% all He-like species:
create_he_modifier ("photo"; photoex);
create_aped_fun ("myphoto_model", default_plasma_state);
fit_fun ("my_photomodel(1, photo(1)) * wabs(1)");
<@@ref>create_aped_funcreate_aped_fun,
he_modifier_init,
he_modifier_init<@@ref>fit_funfit_fun
Geometric dilution factor for a uniform disk
Double_Type[] = W_dilution (x[])
Compute the geometric dilution factor for a mean intensity at position, x=r/rstar from a uniform disk. This is used internally to dilute the radiation field, but may be useful for other purposes. The computed value is
W = (1 - sqrt(1-1/x^2)) /2